Device for measuring the posterior sagittal diameter of a female pelvis



May 16, 1950 E. R. CHAPMAN DEVICE FOR MEASURING THE POSTERIOR SAGITTALDIAMETER A FEMALE PELVIS Filed Feb. 7, 1949 Euyene R. Chapman" [NI/ENTOR BYMM A r TORNE m iatented May '16, 1950 DEVICE FOR -'MEASURINGRQSTERIQR "SAG-ITTAL DIAMETER PELVIS Eugen h. Chapma San An io, App h y7, 1949, Seria 515 916 .4 Cla ms (01. 33 '.1;8)

1 This invention relates :to implfevements in devices for measuringcertain diameters .;Qf the female pelvis and refers more particularly to21 3.? measurement of the posterior sagittal diameter of the pelvis.

When considering questionable .pelvic Qllillet contractions during prenatal examinations. .Qf expectant mothers, the posterior sagit-taldiameter becomes extremely important since it and the transversediameter .of the outlet will ,determine if the patient must undergo .a.Caesarean sectionor can deliver per vaginum in the .normal manner. Theposterior sagittaldiameter is. that distance from the sacro-coccygealjunction or 'joint to a line drawn through the tuberosities ofthe-ischia. It is the present day practice to take this measurementexternally by external palpation. In many instances, this measurementdifficultto make externally for-it is hard to locate :thesacro-coccygeal joint due to the wide variations in the lateral, forwardor backward displacements of the cooc yx in different patients. 'Inaddition, in some women the thickness of the fat pad makes palpationthrough it very difficult. *In any event, this measurement is notaccurate and is at best an estimate for the physician must maize somearbitrary allowance for the thickness of the fat and bone for it is theinner surface of the sacro-coccygeal junction which must be reckonedwith in estimating whether or not the foetus will pass through this partof the birth canal. The pelvirneters heretofore available may not beused to take the measurement of the posterior sagittal diameter of thepelvis directly from the inner surface of the sacro-coccygeal junction.

An object of thi invention is to provide an instrument for measuringdirectly the distance vfrom the inner surface of the sacro-cocoygealjunctign to a line between the tuberosities of the items- A furtherobject is to provide a pelvimeter o! the characte es ribed which may hee m ally manufactured, is easily used, and gives an accurate measurementof the distance-involved.

A still further object is to provide a pelv-imeter of the pivoted armtypehaving two arms formed with special and novel contours which makesit possible to measure.directly the posterior sagittal .diameter.

Other and further objects of thisin'vention will appear from thedescription.

In the a c mpanyin d wing whi h m a part of the instant specification,are to he read in ti e numera ar em oyed t desi nate like parts in t earious .vi ws ,Ei g- .1 is a s hema ic ectional view o a fema e 961 i lutrating a de i e cons i uti enibqcl m m r this invent n n t e sitiolea-.- :tiyeto lhe pelvis to give the desired measure ent; his .2 s a sie ele ation .Q th l ta shcwnin his 1 t ke r-Qm ther erse ide e thepelvimeter to that shown in Fig.1; and

.all s' is a 1 W tak n a pha" he lin ,3 -\3 i thist e. m t on'Q t eaimwsBefwih to th d awin s, and mere anthei anlvF al temal pe t..isshpwnsehematiaits! at .o d r to il ustrat t e purpose and sancti n ohe ne vimet r @119 method h thi inventi n. f lhe diameter for distan eto h mea red sh I; h the in id t fied it? t e numer 5, This 5 h istan[between th cets y a ima n y trahfiters l k tim sities 9 t e isqh a lhpe .et r rrc e s innrises two arms a and .10, h hav hotel centqu s to hhe. inait r mor ifull descr ed r erihs a hanheet en which nermits relatve m v n betwe n th na tsis ztowar thelsiistanee et n tree ends .of the9 and 5 hr hetw h ends pf arms .3 and it that are emate f ets the cann tnn. it has zheeni umi efe able tram the -standpa nt of s1 nlieity and.ecenpmy of struction, to zutihz a p vota cpnnection h twaen thearms byJoining them together with .a sma iboltor pivot .pin J4 and nut J2,

Arm ;9 has a curved portion e 11 adiaeent it ireetendwhich ipresentsalconcave surface ltezthe tree end .of arm ,9. This portion 3a isshaped{to facilitate insertion of the free end pf (arm 9 21 120 the vag-inaiof.a patient with its free end :placed upon .the tissue justoverlying thejsacrorooecygehl "junction. The tissue overlying this junction is 'very.thin, making the inner surface of the tunetion easily detectable :bythe operator. This curved portion also facilitates the orientation lotthe entire instrument in .a .caudad or .cep'ha-lad sense, when taking ameasurement, as will be more fully explained in conjunction with theoperation.

;Arm ;9 has a substantially straight portion 91) adjacent its pivotedend which resides within a plane parallel to and spaced from -a planeineluding the areuate or ,curved pgrtion 9a The wo p ons 9 and a jo nedta h r by 3 hird intermediate portion tth eh 6 5 1 2 9 e niune htherewith, and wherein like refersubstant ally perpendi ularly from thplan ineluding portion 9a. Portion 9b of the arm is spaced laterallyfrom portion 9a in order that the hand of the operator may readily guidethe portion 9a into the position shown in Fig. 1 without interferencedue to the portion 9b because of its lateral or out-of-the-way position.The joining portion 90 preferably is formed with a rather abrupt anglewith each of the other portions of the arm. As viewed in Figs. 1 and 2,it is apparent that the free end of arm 9 is not exactly aligned withportion 9b of the arm, were it extended, but that in addition to beinglaterally spaced therefrom, it is also vertically spaced from such anextension when considered in the plane of the paper in these twofigures. This effects a high position of the pivot in operation whichaids in the proper orientation of the device to place the free end ofarm I!) along the line extending between the tuberosities of the ischia.

I Turning now to arm if], a cross-piece lila preferably is secured tothe free end of the arm to facilitate placement thereof along the linebetween the tuberosities of the ischia. This may be dispensed with andit is contemplated that the cross-piece may be secured to the devicewith a removable mounting. However, it is believed that most physicianswould prefer the device having the cross-piece in place for it doesfacilitate the taking the desired measurement.

When viewed in side elevation as in Figs. 1 and 2, arm H3 is formed witha dog-leg like shape which, together with the lateral off-set of thepivot between arms 9 and it, permits free pivotal movement of arm 10 inoperation, without interference of the hand of the operator which isused in guiding arm 9 into proper location. It is believed that thiswill be well understood by viewing Fig. 1 wherein the hand of theoperator is shown to reside within the angle described by the dog-leglike contour of the device. It is, of course, to be understood that theparticular contour shown is not required but that the arm should beshaped so as to avoid contact with the hand of the operator whichcontrols arm 9 and it has been found that this contour works entirelysatisfactorily. The arm iii, in addition to the cross-piece Illa,includes the portions lflb, I and Hid. The portion [0b carries the freeend of the arm and extends substantialy perpendicularly from cross-piecelOa. This substantially perpendicular portion [0b facilitates properplacement of the free end of the device in operation as it provides astraight length which will extend perpendicularly from the imaginaryline between the tuberosities of the ischia when in proper position. Itis for this reason that the dog-leg like contour is preferable to a widesweeping arc for this purpose.

The portion [9b, of course, resides within a plane which includes thefree end of arm 9.

Inasmuch as this is laterally displaced from the plane including thepivot, it is necessary to provide portion [0c which extends laterallybetween the planes and the portion iild which has a perforate end forreceiving pivot pin l I.

In order that the distance between the ends of the device may be readilydetermined, it is desirable to provide a means which is calibrated toread directly in the desired measurement units.

This may be accomplished by forming at the pivot sociated with the armsof the device adapted to indicate the distance between the two arms.This linkage may include the long pointer arm I4 which is pivoted at oneend to one of the arms and another link l6 pivoted to the other of thetwo arms and to the link at an intermediate point. With thisarrangement, the calibrated scale is in ready view in operation and thescale is made to be operative within the usual range of operation of thedevice. Where the measurement is to be in centimeters, as is the usualcase, the scale can, for instance, range between six centimeters andeleven centimeters.

As viewed in Fig. 2, it is readily apparent that the free end of arm 9is more remote from the pivot than is the free end of arm ID. Thisdifference in the relative displacement of the ends of the two armsprovides for insertion of the arm 9 into the position shown in Fig. 1and proper orientation of arm It as shown with the calibrated scale 15in easy view of an operator.

It is believed that the operation of the device is apparent from theforegoing description. Arm 9 is inserted within the vagina of thepatient and its free end is placed on the sacro-coccygeal junction. Thenthe free end of arm in is placed with the cross-piece Illa in properalignment between the tuberosities of the ischia. The measurement of thedistance between the free ends of the arms is then read from thecalibrated scale [5, pointer l4 indicating the true distance.

In more detail, the recommended procedure involves the insertion of themiddle and index fingers of one hand of the operator into the vagina ofthe patient. In most pre-natal examinations, this is one of the earlysteps taken by the physician in order to examine the character of thebirth passage and this measurement may be taken at that time. The middlefinger is then placed upon the sacro-coccygeal junction and the curvedend of arm 9 is inserted into the vagina and guided into position shownin Fig. 1 with its free end at the extremity of the coccyx. Arm I 0 isthen moved into position between the tuberosities of the ischia, thepivotal connection between the two arms permitting a swinging of arm IDrelative to arm 9 to facilitate its proper orientation. It is oftennecessary to move the entire instrument caudad or cephalad to allow forthe small variation in the horizontal plane of the bi-tuberous diameterin different patients. The curvature of arm 9 is such as to allow forthis movement as the arm crosses the perineum. The measurement is thendetermined by reading the position of the pointer M on the calibratedscale I 5. The device is then removed and may be cleaned and sterilized.

The device may be fabricated of any suitable rigid materials which lendthemselves to the usual methods of sterilization. Stainless steel hasbeen found entirely suitable for this purpose, but it is to beunderstood that any other suitable material may be used.

From the foregoing it will be seen that this invention is one welladapted to attain all of the ends and objects hereinabove set forthtogether with other advantages which are obvious and which are inherentto the structure.

It will be understood that certain features and subcombinations are ofutility and may be employed without reference to other features andsubcombinations. This is contemplated by and .is within the scope of theclaims.

As many possible embodiments may be made of the invention withoutdeparting from the scope thereof, it is to be understood that all matter5 herein set forth or shown in the accompanying drawings is to beinterpreted as illustrative and not in a limiting sense.

The invention having been described, what is claimed is:

1. A pelvimeter comprising two arms having a pivotal connection, one armextending in a curve from one end remote from the pivot, the curvedportion being formed relative to the pivot so as to reside in a singlefiat plane as the arm is swung about the pivot, the corresponding end ofthe second arm being so positioned relative to the pivot that it residesin the same plane as the curved portion of the first arm and ispresented to an intermediate part of said curved portion on its concaveside as the arms are swung together, and calibrated means connected tothe two arms to indicate the distance between said ends of the two arms.

2. A pelvimeter as in claim 1 wherein the second arm is formed with adog-leg like curved contour with the device viewed in side elevation,the dog-leg like curve being such as to present a concave surface to thefirst arm.

3. A pelvimeter as in claim 1 wherein the pivotal connection between thearms is spaced laterall from the plane containing the curved portion ofthe first arm and said end of the second arm, and the second arm isformed with a dogleg like curved contour with the device viewed in sideelevation, the dog-leg like curve being formed so as topresent itsconcave side to the first arm.

4. A pelvimeter as in claim 1 wherein the pivotal connection between thearms is spaced laterally from the plane containing the curved portion ofthe first arm and said end of the second arm, and the first arm has aportion intermediate the pivot and the curved portion and adjacent thecurved portion, which extends abruptly laterally to a plane containingthe pivot, which plane is parallel to said plane containing said ends ofthe arms.

EUGENE R. CHAPMAN.

REFERENCES CITED The following references are of record in the file ofthis patent:

UNITED STATES PATENTS Number Name Date 1,804,064 Sison May 5, 19311,856,295 Sovatkin May 3, 1932 1,953,498 Pieri et a1. Apr. 3, 19342,148,649 Scholl Feb. 28, 1939 2,456,806 Wolffe Dec. 21, 1948

